In recent years, LED chips having high luminance have been developed. Such LED chips are not only used as an illumination for the ten-key pad of a conventional cellular phone or the like or as spot illumination, but also becoming to be used as illumination for a comparatively wide range, e.g., a reading lamp. Accordingly, the LED chips require higher heat radiation properties.
As the first example of a conventional LED device, one described in reference 1 (Japanese Patent Laid-Open No. 7-235696) is available. In this LED device, a through hole is formed in an insulating substrate. One opening of the through hole is covered with a metal plate. A metal film is formed on the wall surface of the through hole, the surface of the metal plate, and the surface of the insulating substrate by plating. An LED chip is mounted on the metal plate and is electrically connected to the metal film on the insulating film by wire bonding.
As the second example of the conventional LED device, one as shown in FIG. 12 is available in which a lead frame 102 formed of a thin metal plate is subjected to resin molding, and an LED chip 103 is mounted on the lead frame 102. More specifically, a funnel-shaped recess 101 is formed in molded resin 100. The lead frame 102 is buried in the bottom of the recess 101. The LED chip 103 is mounted on the lead frame 102 and connected to a terminal portion 104 of the lead frame 102 through a thin metal wire by wire bonding.